Use of an interconnection structure having copper or the like for external connection terminals such as pads may involve performing a surface treatment that covers the surface of the interconnection structure with a metal layer. There are various types of surface treatment, among which electroless nickel plating is mainly used due to its excellent solderability and wire-bonding strength.
In other cases than the use of an interconnection structure for external connection terminals (i.e., in the case of its use in an internal layer), surface treatment that covers a surface with a metal layer may also be used for the purpose of improving reliability through enhanced migration resistance. Electroless nickel plating may be used also in this case.
Electroless nickel plating performed on the surface of an interconnection structure creates a nickel plating film spreading at the bottom, which gives rise to a problem of short-circuiting between interconnections in places where the interconnection pitch is narrow. This is because, while electroless nickel plating requires a pretreatment process of enhancing catalyst activity through adsorption of palladium, this palladium is readily adsorbed on the surface of insulating resin between interconnections, resulting in deposition of an electroless nickel plating film on the surface of insulating resin.
To address this problem, technology has been developed that creates a nickel palladium alloy layer on the surface of insulating resin, followed by performing electroless nickel plating by using the nickel palladium alloy film as a catalyst layer. This technology allows the catalyst activity enhancement step to be omitted, thereby preventing the nickel plating film from having a spreading shape at the bottom (see Patent Document 1, for example).
Use of the above-noted technology to cover the surface of an interconnection structure with a metal layer such as a nickel plating film, however, causes the metal layer to have a flat surface. As a result, provision of insulating resin (e.g., an interlayer insulating layer, underfill resin, or the like) on the metal layer results in the lack of sufficient adhesion between the insulating resin and the interconnection structure.
[Related-Art Documents]
[Patent Document]
[Patent Document 1] Japanese Patent Application Publication No. 62-134990